U.S. patent application number 14/443429 was filed with the patent office on 2015-10-15 for air-conditioning apparatus.
This patent application is currently assigned to Mitsubishi Electric Corporation. The applicant listed for this patent is Hiroyuki OKANO. Invention is credited to Hiroyuki Okano.
Application Number | 20150292777 14/443429 |
Document ID | / |
Family ID | 51020178 |
Filed Date | 2015-10-15 |
United States Patent
Application |
20150292777 |
Kind Code |
A1 |
Okano; Hiroyuki |
October 15, 2015 |
AIR-CONDITIONING APPARATUS
Abstract
A target condensing temperature and a target evaporating
temperature are changed in accordance with a load of each load side
unit obtained by using load detection means, and an operating
frequency of a compressor and a rotation speed of a fan are
controlled such that a condensing temperature obtained by using
temperature detection means coincides with the target condensing
temperature and an evaporating temperature obtained by using the
temperature detection means coincides with the target evaporating
temperature.
Inventors: |
Okano; Hiroyuki; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OKANO; Hiroyuki |
|
|
US |
|
|
Assignee: |
Mitsubishi Electric
Corporation
Tokyo
JP
|
Family ID: |
51020178 |
Appl. No.: |
14/443429 |
Filed: |
December 28, 2012 |
PCT Filed: |
December 28, 2012 |
PCT NO: |
PCT/JP2012/084125 |
371 Date: |
May 18, 2015 |
Current U.S.
Class: |
62/129 |
Current CPC
Class: |
F25B 2400/13 20130101;
F25B 13/00 20130101; F25B 2700/2116 20130101; F25B 2600/0253
20130101; F25B 2600/111 20130101; F25B 2600/21 20130101; Y02B 30/70
20130101; F25B 2700/1933 20130101; F25B 2313/023 20130101; F25B
2313/0294 20130101; F25B 2600/025 20130101; F25B 2313/0314
20130101; F24F 11/85 20180101; F25B 2400/23 20130101; F25B
2313/0233 20130101; F25B 2700/2117 20130101; F25B 2313/0272
20130101; F25B 2700/2104 20130101; F24F 11/77 20180101; F25B 5/02
20130101; F25B 2313/02533 20130101; F25B 2600/19 20130101; F25B
49/02 20130101; F25B 2313/025 20130101; F25B 2313/0293 20130101;
Y02B 30/741 20130101; Y02B 30/746 20130101; F25B 2313/0253
20130101; F25B 2600/112 20130101; F25B 2313/02531 20130101; F25B
2313/0231 20130101; F25B 2313/02741 20130101; F25B 2700/1931
20130101 |
International
Class: |
F25B 5/02 20060101
F25B005/02 |
Claims
1. An air-conditioning apparatus comprising: a heat source side
unit including a compressor and an outdoor heat exchanger connected
in series by piping, the outdoor heat exchanger including a fan,
the heat source side unit being configured to supply heat via
refrigerant; a plurality of load side units each including an
indoor heat exchanger and an indoor expansion device connected in
series by piping, each of the load side units being supplied with
the heat from the heat source side unit via the refrigerant; and a
refrigerant control unit configured to switch a flow of the
refrigerant in accordance with an operating state, wherein the heat
source side unit and the refrigerant control unit are connected in
series by piping, the refrigerant control unit and each load side
unit are connected in series by piping, and the load side units are
connected in parallel by piping, each load side unit performs a
cooling operation or a heating operation, the heat source side unit
includes temperature detection means used for obtaining a
condensing temperature and an evaporating temperature of the
refrigerant, each load side unit includes load detection means used
for obtaining a load during operation, a target condensing
temperature and a target evaporating temperature of the refrigerant
are changed in accordance with the load of each load side unit
obtained by using the load detection means, operating frequency of
the compressor and a rotation speed of the fan are controlled such
that the condensing temperature obtained by using the temperature
detection means coincides with the target condensing temperature
and the evaporating temperature obtained by using the temperature
detection means coincides with the target evaporating
temperature.
2. The air-conditioning apparatus of claim 1, wherein the
temperature detection means includes: a high-pressure sensor
provided in the heat source side unit and configured to detect a
discharge pressure of the refrigerant discharged from the
compressor; and a low-pressure sensor configured to detect a
suction pressure of the refrigerant sucked into the compressor, the
temperature detection means calculates the condensing temperature
from the discharge pressure detected with the high-pressure sensor,
and the temperature detection means calculates the evaporating
temperature from the suction pressure detected with the
low-pressure sensor.
3. The air-conditioning apparatus of claim 1, wherein the load
detection means includes a temperature sensor provided in the load
side unit and configured to detect a load side suction temperature,
and the load detection means detects a load of the load side unit
from a difference between the load side suction temperature and a
set temperature.
4. The air-conditioning apparatus of claim 2, wherein in a heating
only operation mode in which all the load side units perform a
heating operation, and in a heating main operation mode in which
the load side units that perform a heating operation and the load
side units that perform a cooling operation are present together
and a sum of the respective loads of the load side units that
perform the heating operation is higher than a sum of the
respective loads of the load side units that perform the cooling
operation, the condensing temperature is calculated from the
discharge pressure detected with the high-pressure sensor, and the
operating frequency of the compressor is controlled such that the
condensing temperature coincides with the target condensing
temperature, and the evaporating temperature is calculated from the
suction pressure detected with the low-pressure sensor, and the
rotation speed of the fan is controlled such that the evaporating
temperature coincides with the target evaporating temperature.
5. The air-conditioning apparatus of claim 2, wherein in a cooling
only operation mode in which all the load side units perform a
cooling operation, and in a cooling main operation mode in which
the load side units that perform a heating operation and the load
side units that perform a cooling operation are present together
and a sum of the respective loads of the load side units that
perform the cooling operation is higher than a sum of the
respective loads of the load side units that perform the heating
operation, the evaporating temperature is calculated from the
discharge pressure detected with the high-pressure sensor, and the
operating frequency of the compressor is controlled such that the
evaporating temperature coincides with the target evaporating
temperature, and the condensing temperature is calculated from the
suction pressure detected with the low-pressure sensor, and the
rotation speed of the fan is controlled such that the condensing
temperature coincides with the target condensing temperature.
6. The air-conditioning apparatus of claim 4, wherein the heat
source side unit includes a plurality of opening/closing valves and
a plurality of the outdoor heat exchangers, outdoor heat exchanger
units in each of which the opening/closing valve and the outdoor
heat exchanger are connected in series by piping are connected in
parallel by piping, and in the heating only operation mode and in
the heating main operation mode, the opening/closing valves are
controlled in accordance with the target condensing
temperature.
7. The air-conditioning apparatus of claim 5, wherein the heat
source side unit includes a plurality of opening/closing valves and
a plurality of the outdoor heat exchangers, outdoor heat exchanger
units in each of which the opening/closing valve and the outdoor
heat exchanger are connected in series by piping are connected in
parallel by piping, and in the cooling only operation mode and in
the cooling main operation mode, the opening/closing valves are
controlled in accordance with the target evaporating
temperature.
8. The air-conditioning apparatus of claim 2, wherein the load
detection means includes a temperature sensor provided in the load
side unit and configured to detect a load side suction temperature,
and the load detection means detects a load of the load side unit
from a difference between the load side suction temperature and a
set temperature.
9. The air-conditioning apparatus of claim 3, wherein in a heating
only operation mode in which all the load side units perform a
heating operation, and in a heating main operation mode in which
the load side units that perform a heating operation and the load
side units that perform a cooling operation are present together
and a sum of the respective loads of the load side units that
perform the heating operation is higher than a sum of the
respective loads of the load side units that perform the cooling
operation, the condensing temperature is calculated from the
discharge pressure detected with the high-pressure sensor, and the
operating frequency of the compressor is controlled such that the
condensing temperature coincides with the target condensing
temperature, and the evaporating temperature is calculated from the
suction pressure detected with the low-pressure sensor, and the
rotation speed of the fan is controlled such that the evaporating
temperature coincides with the target evaporating temperature.
10. The air-conditioning apparatus of claim 8, wherein in a heating
only operation mode in which all the load side units perform a
heating operation, and in a heating main operation mode in which
the load side units that perform a heating operation and the load
side units that perform a cooling operation are present together
and a sum of the respective loads of the load side units that
perform the heating operation is higher than a sum of the
respective loads of the load side units that perform the cooling
operation, the condensing temperature is calculated from the
discharge pressure detected with the high-pressure sensor, and the
operating frequency of the compressor is controlled such that the
condensing temperature coincides with the target condensing
temperature, and the evaporating temperature is calculated from the
suction pressure detected with the low-pressure sensor, and the
rotation speed of the fan is controlled such that the evaporating
temperature coincides with the target evaporating temperature.
11. The air-conditioning apparatus of claim 3, wherein in a cooling
only operation mode in which all the load side units perform a
cooling operation, and in a cooling main operation mode in which
the load side units that perform a heating operation and the load
side units that perform a cooling operation are present together
and a sum of the respective loads of the load side units that
perform the cooling operation is higher than a sum of the
respective loads of the load side units that perform the heating
operation, the evaporating temperature is calculated from the
discharge pressure detected with the high-pressure sensor, and the
operating frequency of the compressor is controlled such that the
evaporating temperature coincides with the target evaporating
temperature, and the condensing temperature is calculated from the
suction pressure detected with the low-pressure sensor, and the
rotation speed of the fan is controlled such that the condensing
temperature coincides with the target condensing temperature.
12. The air-conditioning apparatus of claim 8, wherein in a cooling
only operation mode in which all the load side units perform a
cooling operation, and in a cooling main operation mode in which
the load side units that perform a heating operation and the load
side units that perform a cooling operation are present together
and a sum of the respective loads of the load side units that
perform the cooling operation is higher than a sum of the
respective loads of the load side units that perform the heating
operation, the evaporating temperature is calculated from the
discharge pressure detected with the high-pressure sensor, and the
operating frequency of the compressor is controlled such that the
evaporating temperature coincides with the target evaporating
temperature, and the condensing temperature is calculated from the
suction pressure detected with the low-pressure sensor, and the
rotation speed of the fan is controlled such that the condensing
temperature coincides with the target condensing temperature.
13. The air-conditioning apparatus of claim 9, wherein the heat
source side unit includes a plurality of opening/closing valves and
a plurality of the outdoor heat exchangers, outdoor heat exchanger
units in each of which the opening/closing valve and the outdoor
heat exchanger are connected in series by piping are connected in
parallel by piping, and in the heating only operation mode and in
the heating main operation mode, the opening/closing valves are
controlled in accordance with the target condensing
temperature.
14. The air-conditioning apparatus of claim 10, wherein the heat
source side unit includes a plurality of opening/closing valves and
a plurality of the outdoor heat exchangers, outdoor heat exchanger
units in each of which the opening/closing valve and the outdoor
heat exchanger are connected in series by piping are connected in
parallel by piping, and in the heating only operation mode and in
the heating main operation mode, the opening/closing valves are
controlled in accordance with the target condensing
temperature.
15. The air-conditioning apparatus of claim 11, wherein the heat
source side unit includes a plurality of opening/closing valves and
a plurality of the outdoor heat exchangers, outdoor heat exchanger
units in each of which the opening/closing valve and the outdoor
heat exchanger are connected in series by piping are connected in
parallel by piping, and in the cooling only operation mode and in
the cooling main operation mode, the opening/closing valves are
controlled in accordance with the target evaporating
temperature.
16. The air-conditioning apparatus of claim 12, wherein the heat
source side unit includes a plurality of opening/closing valves and
a plurality of the outdoor heat exchangers, outdoor heat exchanger
units in each of which the opening/closing valve and the outdoor
heat exchanger are connected in series by piping are connected in
parallel by piping, and in the cooling only operation mode and in
the cooling main operation mode, the opening/closing valves are
controlled in accordance with the target evaporating temperature.
Description
TECHNICAL FIELD
[0001] The present invention relates to a multi-type
air-conditioning apparatus which enables an operation (hereinafter,
referred to as a cooling/heating mixed operation) in which each of
a plurality of indoor units (load side units) performs a cooling
operation or a heating operation, and particularly relates to a
control method which reduces power consumption.
BACKGROUND ART
[0002] Hitherto, there is an air-conditioning apparatus which makes
an evaporating temperature and a condensing temperature, which are
control target temperatures in a refrigeration cycle, variable in
accordance with a load (see Patent Literature 1). The
air-conditioning apparatus performs an operation with a low
compression ratio at the time of low load by making an evaporating
temperature and a condensing temperature, which are control target
temperatures, to be variable values in accordance with an
air-conditioning load estimated based on an operation mode and the
difference between a set temperature and a suction temperature,
thereby reducing power consumption.
[0003] In addition, because of a multi-type, a plurality of indoor
units operate under respective load conditions at the same time,
and the method is a method in which a condensing temperature and an
evaporating temperature of refrigerant are controlled to constant
values, not a method in which a blowout temperature of refrigerant
is controlled for individual indoor units.
[0004] In this method, the difference between the suction
temperature and the set temperature is monitored. When "suction
temperature-set temperature" becomes equal to or less than a
predetermined value, it is determined that the air-conditioning
load is low. If the operation is a cooling operation, by increasing
the evaporating temperature which is a control target, it is
possible to decrease the frequency of a compressor to reduce power
consumption. In addition, if the operation is a heating operation,
by decreasing the condensing temperature which is a control target,
it is possible to decrease the frequency to reduce power
consumption.
CITATION LIST
Patent Literature
[0005] Patent Literature 1: Japanese Unexamined Patent Application
Publication No. 2012-107840 (e.g., see [0014] to [0069] and FIGS. 1
to 10)
SUMMARY OF INVENTION
Technical Problem
[0006] However, when, as in the multi-type air-conditioning
apparatus described in Patent Literature 1 which enables a
cooling/heating mixed operation, the capacity of a heat source side
heat exchanger is controlled in accordance with the load such that
the evaporating temperature and the condensing temperature coincide
with a target evaporating temperature and a target condensing
temperature, if one of these temperatures is controlled, the effect
is not sufficient.
[0007] In addition, there is the following problem. When an
operation is performed in a state where the rotation speed of a fan
at each of a condenser and an evaporator is high in order to
perform control in accordance with the control target condensing
temperature and evaporating temperature, the power consumption of
each fan relatively increases as compared to the power consumption
of a compressor. As a result, an energy-saving effect is
reduced.
[0008] The present invention has been made in order to solve the
above-described problems, and an object of the present invention is
to provide a multi-type air-conditioning apparatus which enables a
cooling/heating mixed operation and controls both an evaporating
temperature and a condensing temperature to increase an
energy-saving effect.
Solution to Problem
[0009] An air-conditioning apparatus according to the present
invention includes: a heat source side unit including a compressor
and an outdoor heat exchanger connected in series by piping, the
outdoor heat exchanger including a fan, the heat source side unit
being configured to supply heat via refrigerant; a plurality of
load side units each including an indoor heat exchanger and an
indoor expansion device connected in series by piping, each of the
load side units being supplied with the heat from the heat source
side unit via the refrigerant; and a refrigerant control unit
configured to switch a flow of the refrigerant in accordance with
an operating state. The heat source side unit and the refrigerant
control unit are connected in series by piping, the refrigerant
control unit and each load side unit are connected in series by
piping, and the load side units are connected in parallel by
piping. Each load side unit performs a cooling operation or a
heating operation. The heat source side unit includes temperature
detection means used for obtaining a condensing temperature and an
evaporating temperature of the refrigerant. Each load side unit
includes load detection means used for obtaining a load during
operation. A target condensing temperature and a target evaporating
temperature of the refrigerant are changed in accordance with the
load of each load side unit obtained by using the load detection
means. An operating frequency of the compressor and a rotation
speed of the fan are controlled such that the condensing
temperature obtained by using the temperature detection means
coincides with the target condensing temperature and the
evaporating temperature obtained by using the temperature detection
means coincides with the target evaporating temperature.
Advantageous Effects of Invention
[0010] With the air-conditioning apparatus according to the present
invention, it is possible to increase an energy-saving effect by
controlling both the evaporating temperature and the condensing
temperature.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a schematic configuration diagram showing an
example of a refrigerant circuit configuration of an
air-conditioning apparatus according to Embodiment of the present
invention.
[0012] FIG. 2 is a refrigerant circuit diagram showing a flow of
refrigerant during a heating only operation mode of the
air-conditioning apparatus according to Embodiment of the present
invention.
[0013] FIG. 3 is a refrigerant circuit diagram showing a flow of
the refrigerant during a heating main operation mode of the
air-conditioning apparatus according to Embodiment of the present
invention.
[0014] FIG. 4 is a refrigerant circuit diagram showing a flow of
the refrigerant during a cooling only operation mode of the
air-conditioning apparatus according to Embodiment of the present
invention.
[0015] FIG. 5 is a refrigerant circuit diagram showing a flow of
the refrigerant during a cooling main operation mode of the
air-conditioning apparatus according to Embodiment of the present
invention.
[0016] FIG. 6 is an explanatory diagram showing control of a fan of
the air-conditioning apparatus according to Embodiment of the
present invention.
DESCRIPTION OF EMBODIMENTS
[0017] Hereinafter, Embodiment of the present invention will be
described with reference to the drawings.
EMBODIMENT
[0018] FIG. 1 is a schematic configuration diagram showing an
example of a refrigerant circuit configuration of an
air-conditioning apparatus 500 according to Embodiment of the
present invention. The refrigerant circuit configuration of the
air-conditioning apparatus 500 will be described with reference to
FIG. 1. It should be noted that the relationship of the size of
each constituent element in the drawings described below including
FIG. 1 may be different from actual size.
[0019] The air-conditioning apparatus 500 is installed in a
building, a condominium, or the like and is able to perform a
cooling/heating mixed operation by utilizing a refrigeration cycle
(heat pump cycle) which circulates refrigerant. The
air-conditioning apparatus 500 includes a heat source side unit
100, a refrigerant control unit 200, and a plurality of (two in
FIG. 1) load side units 300 (300a and 300b).
[0020] In addition, the heat source side unit 100 and the
refrigerant control unit 200 are connected to each other by a
low-pressure pipe 401 and a high-pressure pipe 402, and the
refrigerant control unit 200 and the load side units 300 are
connected to each other by gas pipes 405a and 405b and liquid pipes
406a and 406b, to form the refrigeration cycle.
[0021] [Heat Source Side Unit 100]
[0022] The heat source side unit 100 has a function to supply
cooling energy or heating energy to the load side units 300.
[0023] In FIG. 1, "a" or "b" is added and shown after the reference
signs of some devices included in the "heat source side unit 100".
In the following description, "a" and "b" added after the reference
signs are sometimes omitted, and needless to say, in such a case, a
description is given including the devices of both "a" and
[0024] In the heat source side unit 100, a compressor 101, a
four-way switching valve 102 which is flow path switching means, an
opening/closing valve 105, an outdoor heat exchanger 103 provided
with a fan 106, and an accumulator 104 are provided and connected
in series to form a main refrigerant circuit.
[0025] It should be noted that each of a portion where the
opening/closing valve 105a and the outdoor heat exchanger 103a are
connected in series and a portion where the opening/closing valve
105b and the outdoor heat exchanger 103b are connected in series is
referred to as an outdoor heat exchanger unit.
[0026] In addition, in the heat source side unit 100, check valves
107 to 115 are provided in order to make it possible to cause the
refrigerant to flow in a given direction.
[0027] The check valve 112 is provided on the low-pressure pipe 401
between the refrigerant control unit 200 and the four-way switching
valve 102, the check valve 108 is provided on a connection pipe 403
between the four-way switching valve 102 and the opening/closing
valve 105, and the check valves 107a and 107b are provided on a
connection pipe 404 between the outdoor heat exchanger 103a and a
meeting portion between the two outdoor heat exchangers 103a and
103b.
[0028] Furthermore, the check valve 109 is provided on the
connection pipe 404 between the refrigerant control unit 200 and
the meeting portion between the two outdoor heat exchangers 103a
and 103b, and the check valve 113 is provided on the high-pressure
pipe 402 between the refrigerant control unit 200 and the meeting
portion between the two outdoor heat exchangers 103a and 103b.
[0029] The low-pressure pipe 401 and the high-pressure pipe 402 are
connected to each other by: a first connection pipe 120 which
connects the downstream side of the check valve 112 and the
downstream side of the check valve 113; and a second connection
pipe 121 which connects the upstream side of the check valve 112
and the upstream side of the check valve 113.
[0030] In addition, the connection pipe 403 and the connection pipe
404 are connected to each other by: a third connection pipe 122
which connects the downstream side of the check valve 108 and the
downstream side of the check valve 109; and a fourth connection
pipe 123 which connects the upstream side of the check valve 108
and the upstream side of the check valve 109.
[0031] The check valve 115 is provided on the first connection pipe
120 and permits the refrigerant to flow only in the direction from
the low-pressure pipe 401 to the high-pressure pipe 402, and the
check valve 114 is provided also on the second connection pipe 121
and permits the refrigerant to flow only in the direction from the
low-pressure pipe 401 to the high-pressure pipe 402.
[0032] In addition, the check valve 110 is provided on the third
connection pipe 122 and permits the refrigerant to flow only in the
direction from the connection pipe 404 to the connection pipe 403,
and the check valve 111 is provided also on the fourth connection
pipe 123 and permits the refrigerant to flow only in the direction
from the connection pipe 404 to the connection pipe 403.
[0033] In the heat source side unit 100, a high-pressure sensor 141
is provided between the compressor 101 and the four-way switching
valve 102. Also, a low-pressure sensor 142 is provided between the
four-way switching valve 102 and the accumulator 104.
[0034] The compressor 101 sucks low-temperature and low-pressure
gas refrigerant, compresses the refrigerant into high-temperature
and high-pressure gas refrigerant, and circulates the refrigerant
within the system, thereby causing air-conditioning to be
performed. The compressor 101 may be composed of, for example, a
capacity-controllable inverter-type compressor. However, the
compressor 101 is not limited to the capacity-controllable
inverter-type compressor, and may be a constant-speed-type
compressor or may be a compressor which is a combination of an
inverter-type and a constant-speed-type.
[0035] The four-way switching valve 102 is provided at the
discharge side of the compressor 101, switches a refrigerant flow
path in a cooling operation and a heating operation, and controls a
flow of the refrigerant such that the outdoor heat exchanger 103
serves as an evaporator or a condenser in accordance with an
operation mode.
[0036] The outdoor heat exchanger 103 exchanges heat between a heat
medium (e.g., the ambient air, water, etc.) and the refrigerant,
serves as an evaporator to evaporate and gasify the refrigerant
during a heating operation, and serves as a condenser (radiator) to
condense and liquefy the refrigerant during a cooling operation. If
the outdoor heat exchanger 103 is an air-cooled heat exchanger, the
outdoor heat exchanger 103 is generally provided with the fan 106,
and condensing capacity or evaporating capacity thereof is
controlled based on a rotation speed of the fan 106, command
frequency provided to the fan 106, the power consumption of the fan
106, the value of a current flowing through the fan 106, and the
like.
[0037] In Embodiment, the single fan 106 is provided for the two
outdoor heat exchangers 103a and 103b, but the fan 106 may be
provided for each outdoor heat exchanger 103.
[0038] In addition, in Embodiment, the condensing capacity or
evaporating capacity is controlled based on the rotation speed of
the fan 106.
[0039] The accumulator 104 is provided at the suction side of the
compressor 101 and has a function to store excess refrigerant and a
function to separate liquid refrigerant and gas refrigerant. The
accumulator 104 may be a container capable of storing excess
refrigerant.
[0040] The opening/closing valve 105a is provided at an upstream
portion of the outdoor heat exchanger 103a, and the opening/closing
valve 105b is provided at an upstream portion of the outdoor heat
exchanger 103b, and these opening/closing valves allow the
refrigerant to flow therethrough or does not allow the refrigerant
to flow therethrough by opening/closing thereof being controlled.
That is, the opening/closing valves 105a and 105b adjust the flow
of the refrigerant to the outdoor heat exchanger 103 by
opening/closing thereof being controlled.
[0041] The first connection pipe 120 connects the high-pressure
pipe 402 at the downstream side of the check valve 113 and the
low-pressure pipe 401 at the downstream side of the check valve
112.
[0042] The second connection pipe 121 connects the high-pressure
pipe 402 at the upstream side of the check valve 113 and the
low-pressure pipe 401 at the upstream side of the check valve
112.
[0043] It should be noted that a meeting portion between the second
connection pipe 121 and the high-pressure pipe 402 is shown as a
meeting portion a, a meeting portion between the first connection
pipe 120 and the high-pressure pipe 402 is shown as a meeting
portion b (downstream of the meeting portion a), a meeting portion
between the second connection pipe 121 and the low-pressure pipe
401 is shown in as a meeting portion c, and a meeting portion
between the first connection pipe 120 and the low-pressure pipe 401
is shown as a meeting portion d (downstream of the meeting portion
c).
[0044] The check valve 112 is provided between the meeting portion
c and the meeting portion d and permits the refrigerant to flow
only in the direction from the meeting portion c to the meeting
portion d. The check valve 113 is provided between the meeting
portion a and the meeting portion b and permits the refrigerant to
flow only in the direction from the meeting portion a to the
meeting portion b. The check valve 115 is provided on the first
connection pipe 120 and permits the refrigerant to flow only in the
direction from the meeting portion d to the meeting portion b. The
check valve 114 is provided on the second connection pipe 121 and
permits the refrigerant to flow only in the direction from the
meeting portion c to the meeting portion a.
[0045] The third connection pipe 122 connects the high-pressure
pipe 402 at the downstream side of the check valve 109 and the
connection pipe 403 at the downstream side of the check valve
108.
[0046] The fourth connection pipe 123 connects the connection pipe
404 at the upstream side of the check valve 109 and the connection
pipe 403 at the upstream side of the check valve 108.
[0047] It should be noted that a meeting portion between the fourth
connection pipe 123 and the connection pipe 404 is shown as a
meeting portion e, a meeting portion between the fourth connection
pipe 123 and the high-pressure pipe 402 is shown as a meeting
portion f (downstream of the meeting portion e), a meeting portion
between the fourth connection pipe 123 and the connection pipe 403
is shown as a meeting portion g, and a meeting portion between the
third connection pipe 122 and the connection pipe 403 is shown as a
meeting portion h (downstream of the meeting portion g).
[0048] The check valve 108 is provided between the meeting portion
g and the meeting portion h and permits the refrigerant to flow
only in the direction from the meeting portion g to the meeting
portion h. The check valve 109 is provided between the meeting
portion e and the meeting portion f and permits the refrigerant to
flow only in the direction from the meeting portion e to the
meeting portion f. The check valve 110 is provided on the third
connection pipe 122 and permits the refrigerant to flow only in the
direction from the meeting portion f to the meeting portion h. The
check valve 111 is provided on the fourth connection pipe 123 and
permits the refrigerant to flow only in the direction from the
meeting portion e to the meeting portion g. The check valve 107 is
provided between the outdoor heat exchanger 103 and the meeting
portion e and permits the refrigerant to flow only in the direction
from the outdoor heat exchanger 103 to the meeting portion e.
[0049] The high-pressure sensor 141 is provided at the discharge
side of the compressor 101 and detects the pressure of the
refrigerant discharged from the compressor 101, and the
low-pressure sensor 142 is provided at the suction side of the
compressor 101 and detects the pressure of the refrigerant sucked
into the compressor 101.
[0050] The high-pressure sensor 141 and the low-pressure sensor 142
are used as temperature detection means for obtaining
later-described condensing temperature Tc and evaporating
temperature Te of the refrigerant.
[0051] Pressure information detected by these temperature detection
means is sent to a controller 124 which controls operation of the
air-conditioning apparatus 500, and is used for controlling the
operating frequency of the compressor 101, the rotation speed of
the fan 106, and switching of the four-way switching valve 102.
[0052] [Refrigerant Control Unit 200]
[0053] The refrigerant control unit 200 is provided between the
heat source side unit 100 and the load side unit 300 and switches a
flow of the refrigerant in accordance with operating states of the
load side unit 300.
[0054] It should be noted that in FIG. 1, "a" or "b" is added and
shown after the reference signs of some devices included in the
"refrigerant control unit 200". This indicates being connected to
the "load side unit 300a" described later or being connected to the
"load side unit 300b" described later. In the following
description, "a" and "b" added after the reference signs are
sometimes omitted, and needless to say, in such a case, a
description is given including either device connected to the "load
side unit 300a" or the "load side unit 300b".
[0055] The refrigerant control unit 200 is connected to the heat
source side unit 100 by the high-pressure pipe 402 and the
low-pressure pipe 401 and is connected to the load side unit 300 by
the liquid pipe 406 and the gas pipe 405. The refrigerant control
unit 200 is equipped with a gas-liquid separator 211, a first
opening/closing valve 212 (first opening/closing valves 212a and
212b), a second opening/closing valve 213 (second opening/closing
valves 213a and 213b), a first expansion device 214, a second
expansion device 215, a first refrigerant heat exchanger 216, and a
second refrigerant heat exchanger 217. In addition, a connection
pipe 221 is provided at a primary side of the first refrigerant
heat exchanger 216 and the second refrigerant heat exchanger 217,
and a connection pipe 220 is provided at a secondary side thereof.
It should be noted that the primary side of the first refrigerant
heat exchanger 216 and the second refrigerant heat exchanger 217 is
a side at which liquid refrigerant separated by the gas-liquid
separator 211 flows, and the secondary side thereof is a side at
which refrigerant for subcooling the refrigerant flowing through
the primary side flows via the first expansion device 214 and the
second expansion device 215.
[0056] The gas-liquid separator 211 is provided at a connection
portion between the high-pressure pipe 402 and the connection pipe
221 and has a function to separate the two-phase refrigerant
flowing thereto through the high-pressure pipe 402, into gas
refrigerant and liquid refrigerant. The gas refrigerant separated
by the gas-liquid separator 211 is supplied via the connection pipe
221 to the first opening/closing valve 212, and the liquid
refrigerant separated by the gas-liquid separator 211 is supplied
to the first refrigerant heat exchanger 216.
[0057] The first opening/closing valve 212 serves to control supply
of the refrigerant to the load side unit 300 for each operation
mode and is provided between the connection pipe 221 and the gas
pipe 405. That is, the first opening/closing valve 212 is connected
at one side to the gas-liquid separator 211 and at the other side
to an indoor heat exchanger 312 of the load side unit 300, and
opening/closing thereof is controlled to permit or not permit the
refrigerant to flow therethrough.
[0058] The second opening/closing valve 213 serves to control
supply of the refrigerant to the load side unit 300 for each
operation mode and is provided between the connection pipe 220 and
the gas pipe 405. That is, the second opening/closing valve 213 is
connected at one side to the first refrigerant heat exchanger 216
and at the other side to the indoor heat exchanger 312 of the load
side unit 300, and opening/closing thereof is controlled to permit
or not permit the refrigerant to flow therethrough.
[0059] The first expansion device 214 is provided on the connection
pipe 221 and between the first refrigerant heat exchanger 216 and
the second refrigerant heat exchanger 217, and has functions as a
pressure reducing valve and an expansion valve, and reduces the
pressure of the refrigerant to expand the refrigerant. The first
expansion device 214 may be composed of a device whose opening
degree is variably controllable, for example, an accurate flow rate
control device composed of an electric expansion valve, or cheap
refrigerant flow rate adjusting means such as a capillary tube.
[0060] The second expansion device 215 is provided on the
connection pipe 220 and at the upstream side of the secondary side
of the second refrigerant heat exchanger 217, and has functions as
a pressure reducing valve and an expansion valve, and reduces the
pressure of the refrigerant to expand the refrigerant. Similarly to
the first expansion device 214, the second expansion device 215 may
be composed of a device whose opening degree is variably
controllable, for example, an accurate flow rate control device
composed of an electric expansion valve, or cheap refrigerant flow
rate adjusting means such as a capillary tube.
[0061] The first refrigerant heat exchanger 216 exchanges heat
between the refrigerant flowing at the primary side thereof and the
refrigerant flowing at the secondary side thereof.
[0062] The second refrigerant heat exchanger 217 exchanges heat
between the refrigerant at the primary side thereof and the
refrigerant flowing at the secondary side thereof.
[0063] The refrigerant control unit 200 exchanges heat between the
refrigerant flowing at the primary side and the refrigerant flowing
at the secondary side by the first refrigerant heat exchanger 216
and the second refrigerant heat exchanger 217 to subcool the
refrigerant flowing at the primary side.
[0064] In addition, the refrigerant control unit 200 controls each
bypass amount such that appropriate subcooling is achieved at the
primary side outlet of the first refrigerant heat exchanger 216 by
the opening degree of the first expansion device 214 and
appropriate subcooling is achieved at the primary side outlet of
the second refrigerant heat exchanger 217 by the opening degree of
the second expansion device 215.
[0065] [Load Side Unit 300]
[0066] The load side unit 300 is supplied with cooling energy or
heating energy from the heat source side unit 100 and takes charge
of a cooling load or a heating load.
[0067] It should be noted that in FIG. 1, "a" is added and shown
after the reference sign of each device included in "load side unit
300a", and "b" is added and shown after the reference sign of each
device included in "load side unit 300b". In the following
description, "a" and "b" added after the reference signs are
sometimes omitted, and needless to say, in such a case, each device
is included in not only the load side unit 300a but also the load
side unit 300b.
[0068] In the load side unit 300, the indoor heat exchanger 312
(indoor heat exchangers 312a and 312b) and an indoor expansion
device 311 (indoor expansion devices 311a and 311b) are provided so
as to be connected in series.
[0069] In addition, a temperature sensor 313 (temperature sensors
313a and 313b) is provided between the indoor heat exchanger 312,
and the first opening/closing valve 212 and the second
opening/closing valve 213, and a temperature sensor 314
(temperature sensors 314a and 314b) is provided between the indoor
expansion device 311 and the indoor heat exchanger 312, and a
temperature sensor 315 (temperature sensors 315a and 315b) is
provided at or near the indoor heat exchanger 312.
[0070] It should be noted that a fan which is not shown may be
provided near the indoor heat exchanger 312 for supplying air to
the indoor heat exchanger 312.
[0071] The indoor expansion device 311 has functions as a pressure
reducing valve and an expansion valve and reduces the pressure of
the refrigerant to expand the refrigerant. The indoor expansion
device 311 may be composed of a device whose opening degree is
variably controllable, for example, an accurate flow rate control
device composed of an electric expansion valve, or cheap
refrigerant flow rate adjusting means such as a capillary tube.
[0072] The indoor heat exchanger 312 exchanges heat between a heat
medium (e.g., the ambient air, water, etc.) and the refrigerant,
serves as a condenser (radiator) to condense and liquefy the
refrigerant during a heating operation, and serves as an evaporator
to evaporate and gasify the refrigerant during a cooling operation.
The indoor heat exchanger 312 is generally provided with a fan
which is not shown, and condensing capacity or evaporating capacity
thereof is controlled based on a rotation speed of the fan, command
frequency provided to the fan, the power consumption of the fan,
the value of a current flowing through the fan, and the like.
[0073] It should be noted that in Embodiment, the condensing
capacity or evaporating capacity is controlled based on the
rotation speed of the fan.
[0074] The temperature sensor 313 detects the temperature of a
refrigerant pipe between the indoor heat exchanger 312 and each of
the first opening/closing valve 212 and the second opening/closing
valve 213.
[0075] The temperature sensor 314 detects the temperature of a
refrigerant pipe between the indoor expansion device 311 and the
indoor heat exchanger 312.
[0076] The temperature sensor 315 detects a later-described load
side suction temperature Ta of indoor air at the indoor heat
exchanger 312.
[0077] In addition, information (temperature information) detected
by the temperature sensors 313 to 315 which are load detection
means is sent to the controller 124, which controls operation of
the air-conditioning apparatus 500, and is utilized for controlling
various actuators. That is, the information from the temperature
sensors 313 to 315 is utilized for controlling the opening degree
of the indoor expansion device 311 provided in the load side unit
300, the rotation speed of the fan, which is not shown, and the
like.
[0078] It should be noted that the type of the compressor 101 is
not particularly limited, as long as it is able to compress sucked
refrigerant into a high-pressure state. For example, the compressor
101 may be configured by using various types such as reciprocating,
rotary, scroll, or screw. In addition, the type of the refrigerant
used for the air-conditioning apparatus 500 is not particularly
limited, and natural refrigerant such as carbon dioxide,
hydrocarbon, or helium, chlorine-free alternative refrigerant such
as HFC410A, HFC407C, or HFC404A, or fluorocarbon refrigerant used
for existing products such as R22 or R134a may be used.
[0079] In addition, FIG. 1 shows, as an example, the case where the
heat source side unit 100 is equipped with the controller 124 which
controls operation of the air-conditioning apparatus 500, but the
controller 124 may be provided in either the refrigerant control
unit 200 or the load side unit 300. Alternatively, the controller
124 may be provided outside the heat source side unit 100, the
refrigerant control unit 200, and the load side unit 300. Still
alternatively, the controller 124 may be divided into a plurality
of controllers based on functions thereof, and the respective
controllers may be provided in the heat source side unit 100, the
refrigerant control unit 200, and the load side unit 300. In this
case, the respective controllers may be connected to each other
wirelessly or via wires to be able to communicate with each
other.
[0080] Here, an operation of each mode executed by the
air-conditioning apparatus 500 will be described.
[0081] In the air-conditioning apparatus 500, for example, an
air-conditioning operation is performed upon reception of a cooling
operation request or a heating operation request from a remote
controller installed in a room, and four operation modes
corresponding to these requests are present. The four operation
modes include: a cooling only operation mode in which all of the
load side units 300 make cooling operation requests; a cooling main
operation mode in which cooling operation requests and heating
operation requests are present together, and it is determined that
there are many loads to be handled by a cooling operation (the sum
of respective loads of the load side units 300 that perform a
cooling operation is higher than the sum of respective loads of the
load side units 300 that perform a heating operation); a heating
main operation mode in which cooling operation requests and heating
operation requests are present together, and it is determined that
there are many loads to be handled by a heating operation (the sum
of respective loads of the load side units 300 that perform a
heating operation is higher than the sum of respective loads of the
load side units 300 that perform a cooling operation); and a
heating only operation mode in which all the load side units 300
make heating operation requests.
[0082] [Heating Only Operation Mode]
[0083] FIG. 2 is a refrigerant circuit diagram showing a flow of
the refrigerant during the heating only operation mode of the
air-conditioning apparatus 500 according to Embodiment of the
present invention. An operation during the heating only operation
mode of the air-conditioning apparatus 500 will be described with
reference to FIG. 2.
[0084] The low-temperature and low-pressure refrigerant is
compressed by the compressor 101 into high-temperature and
high-pressure gas refrigerant, and the gas refrigerant is
discharged therefrom. The high-temperature and high-pressure gas
refrigerant discharged from the compressor 101 flows via the
four-way switching valve 102, passes through the check valve 115
and flows through the high-pressure pipe 402 to flow out from the
heat source side unit 100 to the refrigerant control unit 200.
[0085] The gas refrigerant having flowed into the refrigerant
control unit 200 flows into the gas-liquid separator 211 and flows
through the connection pipe 221 to the first opening/closing valve
212. At that time, the first opening/closing valve 212 is opened,
and the second opening/closing valve 213 is closed. Then, the
high-temperature and high-pressure gas refrigerant having passed
through the first opening/closing valve 212 flows through the gas
pipe 405 to flow out from the refrigerant control unit 200 to the
load side unit 300.
[0086] The gas refrigerant having flowed into the load side unit
300 flows into the indoor heat exchanger 312 (the indoor heat
exchanger 312a and the indoor heat exchanger 312b). Since the
indoor heat exchanger 312 serves as a condenser, the refrigerant
exchanges heat with the ambient air to condense and liquefy. At
that time, the refrigerant rejects heat, whereby an air-conditioned
space such as the interior of a room is heated. Thereafter, the
liquid refrigerant having flowed out from the indoor heat exchanger
312 is reduced in pressure by the indoor expansion device 311 (the
indoor expansion device 311a and the indoor expansion device 311b)
and flows through the liquid pipe 406 (the liquid pipe 406a and the
liquid pipe 406b) to flow out from the load side unit 300 to the
refrigerant control unit 200.
[0087] The liquid refrigerant having flowed into the refrigerant
control unit 200 passes through the second expansion device 215 and
flows through the connection pipe 220 to the low-pressure pipe 401.
Then, the liquid refrigerant flows through the low-pressure pipe
401 to flow out from the refrigerant control unit 200, and returns
to the heat source side unit 100.
[0088] The refrigerant having returned to the heat source side unit
100 passes through the check valve 114 and the check valve 110 to
the outdoor heat exchanger 103 (the outdoor heat exchanger 103a and
the outdoor heat exchanger 103b). At that time, the opening/closing
valve 105 is opened. Since the outdoor heat exchanger 103 serves as
an evaporator, the refrigerant exchanges heat with the ambient air
to evaporate and gasify. Thereafter, the gas refrigerant having
flowed out from the outdoor heat exchanger 103 flows via the
four-way switching valve 102 into the accumulator 104. Then, the
gas refrigerant within the accumulator 104 is sucked into the
compressor 101 and circulated within the system, whereby a
refrigeration cycle is established.
[0089] Through the above flow, the air-conditioning apparatus 500
executes the heating only operation mode.
[0090] During the heating only operation mode, the operating
frequency of the compressor 101 is controlled such that the
condensing temperature Tc calculated from a discharge pressure (of
the refrigerant discharged from the compressor 101) detected with
the high-pressure sensor 141, which is the temperature detection
means, coincides with a target condensing temperature Tcm. In
addition, the rotation speed of the fan 106 is controlled such that
the evaporating temperature Te calculated from a suction pressure
(of the refrigerant sucked into the compressor 101) detected with
the low-pressure sensor 142, which is the temperature detection
means, coincides with a target evaporating temperature Tem.
[0091] Therefore, if a heating load increases with the operating
frequency of the compressor 101 kept constant, the condensing
temperature Tc decreases. Then, the target condensing temperature
Tcm is increased and the operating frequency of the compressor 101
is increased such that the condensing temperature Tc coincides with
Tcm, thereby achieving an operation of increasing the heating
capacity.
[0092] Conversely, if a heating load decreases with the operating
frequency of the compressor 101 kept constant, the condensing
temperature Tc increases. Then, the target condensing temperature
Tcm is decreased and the operating frequency of the compressor 101
is deceased such that the condensing temperature Tc coincides with
Tcm, thereby achieving an operation of decreasing the heating
capacity. Thus, it is possible to reduce the power consumption.
[0093] In addition, a load of the load side unit 300 is obtained
based on the difference .DELTA.Th between a set temperature To and
the load side suction temperature Ta of the indoor air at the
indoor heat exchanger 312 which is detected with the temperature
sensor 315, which is the load detection means. If the heating load
decreases, the load side suction temperature Ta and the set
temperature To are close to each other. Then, if the temperature
difference .DELTA.Th=To-Ta during the heating operation is less
than a predetermined value .DELTA.Tho (.DELTA.Th<.DELTA.Tho), it
is determined that the load is low, and a target condensing
temperature initial value Tcm0 is changed to a target condensing
temperature change value Tcm1. At that time, Tcm1 may be a fixed
value, or may be a function of the temperature difference
.DELTA.Th, but Tcm0>Tcm1. Here, Ta may be an arithmetic mean or
may be a weighted mean based on capacity when a plurality of the
load side units 300 operate. In addition, for Ta, the load side
unit 300 having a maximum temperature difference .DELTA.Th among
the connected load side units 300 may be selected as a
representative one.
[0094] In any of the cases, Tcm0 becomes Tcm1 (<Tcm0), and the
operating frequency of the compressor 101 decreases according to
the target. Thus, it is possible to reduce the power
consumption.
[0095] It should be noted that the outdoor heat exchanger 103 is
configured to be able to control a flow of the refrigerant flowing
through the outdoor heat exchanger 103 by an opening/closing
operation of the opening/closing valve 105. In Embodiment, the
outdoor heat exchanger 103 is configured to be divided into the two
outdoor heat exchangers 103a and 103b as shown in FIG. 2, but may
be configured with three or more outdoor heat exchangers by
providing the opening/closing valve 105 and the check valve 107 in
front of and in rear of the outdoor heat exchanger 103.
[0096] That is, opening/closing of each opening/closing valve 105
is controlled in accordance with the load of the load side unit 300
to select a volume of the outdoor heat exchanger 103 which
exchanges heat (the number of the outdoor heat exchangers 103 into
which the refrigerant is caused to flow), and if the division
number increases, the number of volumes to be selected also
increases.
[0097] In addition, when a heating load is low, the maximum volume
may be selected as the volume of the outdoor heat exchanger 103.
That is, in FIG. 2, the opening/closing valves 105a and 105b are
opened to increase the heat exchange volume. By so doing, when the
heating load is low, even if the rotation speed of the fan 106 is
made minimum, it is possible to cause the evaporating temperature
Te to coincide with the target evaporating temperature Tem, and
thus it is possible to reduce the power consumption of the fan
106.
[0098] Because of the above, the operating frequency of the
compressor 101 is controlled such that the condensing temperature
Tc coincides with the target condensing temperature Tcm, and the
rotation speed of the fan 106 is controlled such that the
evaporating temperature Te coincides with the target evaporating
temperature Tem.
[0099] Thus, if the heating load decreases with the operating
frequency of the compressor 101 kept constant, the condensing
temperature Tc increases. Then, the target condensing temperature
Tcm is decreased and the operating frequency of the compressor 101
is decreased such that the condensing temperature Tc coincides with
Tcm, thereby achieving an operation of decreasing the heating
capacity. Thus, it is possible to reduce the power consumption.
[0100] In addition, when the heating load is low, the load side
suction temperature Ta and the set temperature To are close to each
other. Thus, if the temperature difference .DELTA.Th=To-Ta during
the heating operation is less than the predetermined value
.DELTA.Tho, it is determined that the load is low, and the target
condensing temperature initial value Tcm0 is changed to the target
condensing temperature change value Tcm1 (<Tcm0). By so doing,
the operating frequency of the compressor 101 decreases according
to the target. Thus, it is possible to reduce the power
consumption.
[0101] In addition, when the heating load is low, the maximum
volume is selected as the volume of the outdoor heat exchanger 103.
By so doing, when the heating load is low, it is possible to cause
the evaporating temperature Te to coincide with the target
evaporating temperature Tem even if the rotation speed of the fan
106 is made minimum. Thus, it is possible to reduce the power
consumption of the fan 106.
[0102] It should be noted that even when the heating load is high,
by decreasing the operating frequency of the compressor 101, it is
possible to reduce the power consumption, but the heating capacity
also decreases at the same time. Thus, the case where the heating
load is low and the heating capacity is not required is determined,
and an efficient operation is performed at that time.
[0103] In Embodiment, an air-cooled type is taken as an example,
and the rotation speed of the fan 106 is monitored, but a
water-cooled type may be taken as an example, a water pump control
value (frequency, power consumption, current) may be monitored for
controlling the opening/closing valves 105a and 105b.
[0104] By performing control as described above, it is possible to
obtain an air-conditioning apparatus 500 having a high
energy-saving effect.
[0105] In addition, when a cooling operation and a heating
operation are present together as operation requests provided to
the air-conditioning apparatus 500 and it is determined that a load
to be processed by the heating operation is higher, the operation
mode becomes the heating main operation mode.
[0106] [Heating Main Operation Mode]
[0107] FIG. 3 is a refrigerant circuit diagram showing a flow of
the refrigerant during the heating main operation mode of the
air-conditioning apparatus 500 according to Embodiment of the
present invention. An operation during the heating main operation
mode of the air-conditioning apparatus 500 will be described with
reference to FIG. 3. Here, the heating main operation mode when
there is a heating request from the load side unit 300a and a
cooling request from the load side unit 300b, will be
described.
[0108] It should be noted that a flow of the refrigerant to the
load side unit 300a, from which there is the heating request is the
same as that during the heating only operation mode, and thus the
description thereof is omitted.
[0109] The liquid refrigerant flowing through the liquid pipe 406a
is subcooled by the second refrigerant heat exchanger 217, and then
flows through the liquid pipe 406b to the load side unit 300b from
which there is the cooling request. The liquid refrigerant having
flowed into the load side unit 300b is reduced in pressure by the
indoor expansion device 311b. The liquid refrigerant reduced in
pressure by the indoor expansion device 311b flows into the indoor
heat exchanger 312b. Since the indoor heat exchanger 312b serves as
an evaporator, the liquid refrigerant exchanges heat with the
ambient air to evaporate and gasify. At that time, the refrigerant
receives heat from the surroundings, whereby the interior of the
room is cooled. Thereafter, the gas refrigerant having flowed out
from the load side unit 300b passes through the second
opening/closing valve 213b and flows through the connection pipe
220. The gas refrigerant meets the refrigerant that has flowed
through the connection pipe 220 by passing through the first
expansion device 214 and the second expansion device 215 in order
to be subcooled by the second refrigerant heat exchanger 217, to
become two-phase gas-liquid refrigerant, then flows through the
low-pressure pipe 401 to flow out from the refrigerant control unit
200, and returns to the heat source side unit 100.
[0110] The two-phase gas-liquid refrigerant having returned to the
heat source side unit 100 passes through the check valve 114 and
the check valve 110 to the outdoor heat exchanger 103 (the outdoor
heat exchanger 103a and the outdoor heat exchanger 103b). At that
time, the opening/closing valve 105a is opened. Since the outdoor
heat exchanger 3 serves as an evaporator, the two-phase gas-liquid
refrigerant exchanges heat with the ambient air to evaporate and
gasify. Thereafter, the gas refrigerant having flowed out from the
outdoor heat exchanger 103 flows via the four-way switching valve
102 into the accumulator 104. Then, the gas refrigerant within the
accumulator 104 is sucked into the compressor 101 and circulated
within the system, whereby a refrigeration cycle is established.
Through the above flow, the air-conditioning apparatus 500 executes
the heating main operation mode.
[0111] In the heating main operation mode as well, similarly to the
heating only operation mode, by changing the target condensing
temperature Tcm and the target evaporating temperature Tem in
accordance with the heating load, it is possible to reduce the
power consumption.
[0112] By performing control as described above, it is possible to
obtain an air-conditioning apparatus 500 having a high
energy-saving effect.
[0113] It should be noted that in Embodiment, the case has been
shown in which there are the single heat source side unit 100, the
single refrigerant control unit 200, and the two load side units
300, but the number of each kinds of units is not particularly
limited. In addition, in Embodiment, the case where the present
invention is applied to the air-conditioning apparatus 500 has been
described, but the present invention is also applicable to another
system that forms a refrigerant circuit by using a refrigeration
cycle, such as a refrigerating system.
[0114] [Cooling Only Operation Mode]
[0115] FIG. 4 is a refrigerant circuit diagram showing a flow of
the refrigerant during the cooling only operation mode of the
air-conditioning apparatus 500 according to Embodiment of the
present invention. An operation during the cooling only operation
mode of the air-conditioning apparatus 500 will be simply described
with reference to FIG. 4.
[0116] The low-temperature and low-pressure refrigerant is
compressed by the compressor 101 into high-temperature and
high-pressure gas refrigerant, and the gas refrigerant is
discharged therefrom. The high-temperature and high-pressure gas
refrigerant discharged from the compressor 101 flows via the
four-way switching valve 102 and passes through the check valve 108
to the opening/closing valve 105. At that time, the opening/closing
valve 105 is opened. Then, the gas refrigerant having passed
through the opening/closing valve 105 flows to the outdoor heat
exchanger 103. Since the outdoor heat exchanger 103 serves as a
condenser, the gas refrigerant exchanges heat with the ambient air
to condense and liquefy. Thereafter, the high-pressure liquid
refrigerant having flowed out from the outdoor heat exchanger 103
flows through the connection pipe 404, passes through the check
valve 109 and the check valve 113, and flows through the
high-pressure pipe 402 to flow out from the heat source side unit
100 to the refrigerant control unit 200.
[0117] The liquid refrigerant having flowed into the refrigerant
control unit 200 flows into the gas-liquid separator 211 and flows
into the primary side of the first refrigerant heat exchanger 216.
There, the liquid refrigerant is subcooled by the refrigerant
flowing through the secondary side of the first refrigerant heat
exchanger 216. The liquid refrigerant having an increased degree of
subcooling is reduced in pressure to an intermediate pressure by
the first expansion device 214. Then, the liquid refrigerant flows
to the second refrigerant heat exchanger 217 and is further
subcooled. Thereafter, the liquid refrigerant divides, and part
thereof flows through the liquid pipe 406 (the liquid pipe 406a and
the liquid pipe 406b) to flow out from the refrigerant control unit
200 to the load side unit 300.
[0118] The liquid refrigerant having flowed into the load side unit
300 is reduced in pressure by the indoor expansion device 311 (the
indoor expansion device 311a and the indoor expansion device 311b)
and becomes low-temperature and two-phase gas-liquid refrigerant.
The low-temperature and two-phase gas-liquid refrigerant flows into
the indoor heat exchanger 312 (the indoor heat exchanger 312a and
the indoor heat exchanger 312b). Since the indoor heat exchanger
312 serves as an evaporator, the refrigerant exchanges heat with
the ambient air to evaporate and gasify. At that time, the
refrigerant receives heat from the surroundings, whereby the
interior of the room is cooled. Thereafter, the gas refrigerant
having flowed out from the indoor heat exchanger 312 flows through
the gas pipe 405 (the gas pipe 405a and the gas pipe 405b) to flow
out from the load side unit 300 to the refrigerant control unit
200.
[0119] The gas refrigerant having flowed into the refrigerant
control unit 200 flows to the second opening/closing valve 213. At
that time, the second opening/closing valve 213 is opened, and the
first opening/closing valve 212 is closed. Then, the gas
refrigerant having passed through the second opening/closing valve
213 meets the refrigerant that has flowed through the connection
pipe 220 by passing through the first expansion device 214 and the
second expansion device 215 in order to be subcooled by the second
refrigerant heat exchanger 217, then flows through the low-pressure
pipe 401 to flow out from the refrigerant control unit 200, and
returns to the heat source side unit 100.
[0120] The gas refrigerant having returned to the heat source side
unit 100 passes through the check valve 112 and flows via the
four-way switching valve 102 into the accumulator 104. Then, the
gas refrigerant within the accumulator 104 is sucked into the
compressor 101 and circulated within the system, whereby a
refrigeration cycle is established. Through the above flow, the
air-conditioning apparatus 500 executes the cooling only operation
mode.
[0121] During the cooling only operation mode, the operating
frequency of the compressor 101 is controlled such that the
evaporating temperature Te calculated from the suction pressure (of
the refrigerant sucked into the compressor 101) detected with the
low-pressure sensor 142, which is the temperature detection means,
coincides with the target evaporating temperature Tem. In addition,
the rotation speed of the fan 106 is controlled such that the
condensing temperature Tc calculated from the discharge pressure
(of the refrigerant discharged from the compressor 101) detected
with the high-pressure sensor 141, which is the temperature
detection means, coincides with the target condensing temperature
Tcm.
[0122] Therefore, if a cooling load increases with the operating
frequency of the compressor 101 kept constant, the evaporating
temperature Te increases. Then, the target evaporating temperature
Tem is decreased and the operating frequency of the compressor 101
is increased such that the evaporating temperature Te coincides
with Tem, thereby achieving an operation of increasing the cooling
capacity.
[0123] Conversely, if a cooling load decreases with the operating
frequency of the compressor 101 kept constant, the evaporating
temperature Te decreases. Then, the target evaporating temperature
Tem is increased and the operating frequency of the compressor 101
is decreased such that the evaporating temperature Te coincides
with Tem, thereby achieving an operation of decreasing the cooling
capacity. Thus, it is possible to reduce the power consumption.
[0124] A load of the load side unit 300 is obtained based on the
difference .DELTA.Tc between the set temperature To and the load
side suction temperature Ta of the indoor air which is detected
with the temperature sensor 315, which is the load detection means.
If the heating load decreases, the load side suction temperature Ta
and the set temperature To are close to each other. Then, if the
temperature difference .DELTA.Tr=Ta-To during the cooling operation
is less than a predetermined value .DELTA.Tro (.DELTA.Tr 21
.DELTA.Tro), it is determined that the load is low, and a target
evaporating temperature initial value Tem0 is changed to a target
evaporating temperature change value Tem1. At that time, Tem1 may
be a fixed value, or may be a function of the temperature
difference .DELTA.Tr, but Tem0<Tem1. Here, Ta may be an
arithmetic mean or may be a weighted mean based on capacity when a
plurality of the load side units 300 operate. In addition, for Ta,
the load side unit 300 having a maximum temperature difference
.DELTA.Tr among the connected load side units 300 may be selected
as a representative one. In any of the cases, Tem0 becomes Tem1
(>Tem0), and the operating frequency of the compressor 101
decreases according to a target. Thus, it is possible to reduce the
power consumption.
[0125] In addition, when a cooling load is low, the maximum volume
may be selected as the volume of the outdoor heat exchanger 103.
That is, in FIG. 4, the opening/closing valves 105a and 105b are
opened to increase the heat exchange volume. By so doing, when the
cooling load is low, even if the rotation speed of the fan 106 is
made minimum, it is possible to cause the condensing temperature Tc
to coincide with the target condensing temperature Tcm, and thus it
is possible to reduce the power consumption of the fan 106.
[0126] Because of the above, the operating frequency of the
compressor 101 is controlled such that the evaporating temperature
Te coincides with the target evaporating temperature Tem, and the
rotation speed of the fan 106 is controlled such that the
condensing temperature Tc coincides with the target condensing
temperature Tcm.
[0127] Thus, if the cooling load decreases with the operating
frequency of the compressor 101 kept constant, the evaporating
temperature Te decreases. Then, the target evaporating temperature
Tem is increased and the operating frequency of the compressor 101
is decreased such that the evaporating temperature Te coincides
with Tem, thereby achieving an operation of decreasing the cooling
capacity. Thus, it is possible to reduce the power consumption.
[0128] In addition, when the cooling load is low, the load side
suction temperature Ta and the set temperature To are close to each
other. Thus, if the temperature difference .DELTA.Tr=To-Ta during
the cooling operation is less than the predetermined value
.DELTA.Tro, it is determined that the load is low, and the target
evaporating temperature initial value Tem0 is changed to the target
evaporating temperature change value Tem1 (>Tem0). By so doing,
the operating frequency of the compressor 101 decreases according
to the target. Thus, it is possible to reduce the power
consumption.
[0129] In addition, when the cooling load is low, the maximum
volume is selected as the volume of the outdoor heat exchanger 103.
By so doing, when the cooling load is low, it is possible to cause
the condensing temperature Tc to coincide with the target
condensing temperature Tcm even if the rotation speed of the fan
106 is made minimum. Thus, it is possible to reduce the power
consumption of the fan 106.
[0130] It should be noted that even when the cooling load is high,
by decreasing the operating frequency of the compressor 101, it is
possible to reduce the power consumption, but the cooling capacity
also decreases at the same time, thus the case where the cooling
load is low and the cooling capacity is not required is determined,
and an efficient operation is performed at that time.
[0131] By performing control as described above, it is possible to
obtain an air-conditioning apparatus 500 having a high
energy-saving effect.
[0132] [Cooling Main Operation Mode]
[0133] FIG. 5 is a refrigerant circuit diagram showing a flow of
the refrigerant during the cooling main operation mode of the
air-conditioning apparatus 500 according to Embodiment of the
present invention. An operation during the cooling main operation
mode of the air-conditioning apparatus 500 will be simply described
with reference to FIG. 5. Here, the cooling main operation mode
when there is a cooling request from the load side unit 300a and a
heating request from the load side unit 300b, will be
described.
[0134] The low-temperature and low-pressure refrigerant is
compressed by the compressor 101 into high-temperature and
high-pressure gas refrigerant, and the gas refrigerant is
discharged therefrom. The high-temperature and high-pressure gas
refrigerant discharged from the compressor 101 flows via the
four-way switching valve 102 and passes through the check valve 108
to the opening/closing valve 105. At that time, the opening/closing
valve 105 is opened. Then, the gas refrigerant having passed
through the opening/closing valve 105 flows to the outdoor heat
exchanger 103. Since the outdoor heat exchanger 103 serves as a
condenser, the gas refrigerant exchanges heat with the ambient air
to condense and liquefy. Thereafter, the high-pressure two-phase
gas-liquid refrigerant having flowed out from the outdoor heat
exchanger 103 flows through the connection pipe 404, passes through
the check valve 109 and the check valve 113, and flows through the
high-pressure pipe 402 to flow out from the heat source side unit
100 to the refrigerant control unit 200.
[0135] The two-phase gas-liquid refrigerant having flowed into the
refrigerant control unit 200 flows into the gas-liquid separator
211 and is separated into gas refrigerant and liquid refrigerant by
the gas-liquid separator 211. After the separation, the gas
refrigerant flows out from the gas-liquid separator 211 and flows
through the connection pipe 221 to the first opening/closing valve
212. At that time, the first opening/closing valve 212a is closed,
and the first opening/closing valve 212b is opened. Then, the gas
refrigerant having passed through the first opening/closing valve
212b flows through the gas pipe 405b into the load side unit 300b.
The gas refrigerant having flowed into the load side unit 300b
rejects heat to the surroundings at the indoor heat exchanger 312b
thereby heating the air-conditioned space and condensing and
liquefying. At that time, the refrigerant receives heat from the
surroundings, whereby the interior of the room is cooled.
Thereafter, the liquid refrigerant having flowed out from the
indoor heat exchanger 312b is reduced in pressure to an
intermediate pressure by the indoor expansion device 311b.
[0136] The intermediate-pressure liquid refrigerant reduced in
pressure by the indoor expansion device 311b flows through the
liquid pipe 406b into the second refrigerant heat exchanger 217.
There, the liquid refrigerant meets the liquid refrigerant that has
been separated by the gas-liquid separator 211, has flowed through
the first refrigerant heat exchanger 216, has passed through the
first expansion device 214, and has flowed into the second
refrigerant heat exchanger 217. Then, the liquid refrigerant having
a degree of subcooling increased further by the second refrigerant
heat exchanger 217 flows through the liquid pipe 406a to flow out
from the refrigerant control unit 200 to the load side unit
300a.
[0137] The liquid refrigerant having flowed into the load side unit
300 is reduced in pressure by the indoor expansion device 311a and
becomes low-temperature and two-phase gas-liquid refrigerant. The
low-temperature and two-phase gas-liquid refrigerant flows into the
indoor heat exchanger 312a. Since the indoor heat exchanger 312a
serves as an evaporator, the refrigerant exchanges heat with the
ambient air to evaporate and gasify. At that time, the refrigerant
receives heat from the surroundings, whereby the interior of the
room is cooled. Thereafter, the gas refrigerant having flowed out
from the indoor heat exchanger 312a flows through the gas pipe 405a
to flow out from the load side unit 300 to the refrigerant control
unit 200.
[0138] The gas refrigerant having flowed into the refrigerant
control unit 200 flows to the second opening/closing valve 213. At
that time, the second opening/closing valve 213a is opened, and the
second opening/closing valve 213b is closed. Then, the gas
refrigerant having passed through the second opening/closing valve
213a meets the refrigerant that has flowed through the connection
pipe 220 by passing through the first expansion device 214 and the
second expansion device 215 in order to be subcooled by the second
refrigerant heat exchanger 217, then flows through the low-pressure
pipe 401 to flow out from the refrigerant control unit 200, and
returns to the heat source side unit 100.
[0139] The gas refrigerant having returned to the heat source side
unit 100 passes through the check valve 112 and flows via the
four-way switching valve 102 into the accumulator 104. Then, the
gas refrigerant within the accumulator 104 is sucked into the
compressor 101 and circulated within the system, whereby a
refrigeration cycle is established. Through the above flow, the
air-conditioning apparatus 500 executes the cooling main operation
mode.
[0140] During the cooling main operation mode, the rotation speed
of the fan 106 is controlled toward the target condensing
temperature Tcm.
[0141] When the heating load is low, the load side suction
temperature Ta during the heating operation and the set temperature
To are close to each other. Therefore, similarly to the heating
only operation mode, if the temperature difference .DELTA.Th=To-Ta
is less than the predetermined value .DELTA.Tho, it is determined
that the load is low, and the target condensing temperature initial
value Tcm0 is changed to the target condensing temperature change
value Tcm1. At that time, Tcm1 may be a fixed value, or may be a
function of the temperature difference .DELTA.T, but Tcm0>Tcm1.
Here, Ta may be an arithmetic mean or may be a weighted mean based
on capacity when a plurality of the load side units 300 operate. In
addition, for Ta, the load side unit 300 having a maximum
temperature difference .DELTA.Tc among the connected load side
units 300 may be selected as a representative one. In any of the
cases, Tcm0 becomes Tcm1 (<Tcm0).
[0142] At that time, the volume of the outdoor heat exchanger 103
executes control of the opening/closing valve 105b in accordance of
the target condensing temperature Tcm. By decreasing the heat
transfer area of the outdoor heat exchanger 103, the condensing
temperature Tc is kept high, but when the load is low, it is
necessary to increase the rotation speed of the fan 106, and thus
it is desirable to increase the heat transfer area of the outdoor
heat exchanger 103.
[0143] FIG. 6 is an explanatory diagram showing control of the fan
of the air-conditioning apparatus according to Embodiment of the
present invention.
[0144] For example, as shown in FIG. 6, control is performed as
follows. If it is determined that the heating load is high, the
opening/closing valve 105b is closed, the heat transfer area of the
outdoor heat exchanger 103 is decreased, and the rotation speed of
the fan 106 is decreased. If it is determined that the heating load
is low, the opening/closing valve 105b is opened, the heat transfer
area of the outdoor heat exchanger 103 is increased, and the
rotation speed of the fan 106 is decreased.
[0145] It should be noted that the opening/closing valve 105a is
opened in any of the cases.
[0146] By performing control as described above, it is possible to
obtain an air-conditioning apparatus 500 having a high
energy-saving effect.
REFERENCE SIGNS LIST
[0147] 100 heat source side unit 101 compressor 102 four-way
switching valve 103 outdoor heat exchanger 103a outdoor heat
exchanger 103b outdoor heat exchanger 104 accumulator 105
opening/closing valve 105a opening/closing valve 105b
opening/closing valve 106 fan 107 check valve 107a check valve 107b
check valve 108 check valve 109 check valve 110 check valve 111
check valve 112 check valve 113 check valve 114 check valve 115
check valve 120 first connection pipe 121 second connection pipe
122 third connection pipe 123 fourth connection pipe 124 controller
141 high-pressure sensor 142 low-pressure sensor 200 refrigerant
control unit 211 gas-liquid separator 212 first opening/closing
valve 212a first opening/closing valve 212b first opening/closing
valve 213 second opening/closing valve 213a second opening/closing
valve 213b second opening/closing valve 214 first expansion device
215 second expansion device 216 first refrigerant heat exchanger
217 second refrigerant heat exchanger 220 connection pipe 221
connection pipe 300 load side unit 300a load side unit 300b load
side unit 311 indoor expansion device 311a indoor expansion device
311b indoor expansion device 312 indoor heat exchanger 312a indoor
heat exchanger 312b indoor heat exchanger 313 temperature sensor
313a temperature sensor 313b temperature sensor 314 temperature
sensor 314a temperature sensor 314b temperature sensor 315
temperature sensor 315a temperature sensor 315b temperature sensor
300 load side unit 300a load side unit 300b load side unit 401
low-pressure pipe 402 high-pressure pipe 403 connection pipe 404
connection pipe 405 gas pipe 405a gas pipe 405b gas pipe 406 liquid
pipe 406a liquid pipe 406b liquid pipe 500 air-conditioning
apparatus a meeting portion b meeting portion c meeting portion d
meeting portion e meeting portion f meeting portion g meeting
portion h meeting portion
* * * * *